Aaron Copland may be one of the most under-appreciated composers of the 20th century. Not in terms of exposure, but in the way so much of his output remains buried beneath the blockbusting popularity of works like Billy the Kid or Rodeo. Leonard Slatkin's programme with the Philharmonia, part of the celebrations marking Copland's centenary year, was a super-abundant attempt to represent every side of Copland's creativity, and to put the historical record straight.

Connotations, written in 1962 for the opening of New York's Lincoln Center, was the least well-known and most "difficult" work in the concert. On the surface, this 20-minute orchestral essay belongs to Copland's abstract style. But in reality, Connotations is a post-romantic orchestral showpiece, complete with batteries of percussion and impassioned string lines. For all its pervasive dissonance, the shape and flow of the music are grounded in conventional idioms.

Hearing Connotations just after Appalachian Spring revealed that although Copland's oeuvre may seem to contain a schizophrenic split between abstraction and accessibility, there is a genuine continuity between all of his works. The same concern for clarity defines the orchestration of Connotations as it does the wide-open harmonies at the end of Appalachian Spring.

If there is one piece which embodies the gamut of Copland's compositional continuum, it is his settings of poems by Emily Dickinson. Responding to Dickinson's lucid imagery, Copland employed the range of his creative techniques to depict nature's glories and the inevitability of death. Soprano Barbara Bonney was ideally attuned to the vivid spirituality of the music. The Philharmonia conjured a soundworld of Mahlerian subtlety, from impetuous birds to the tread of death's carriage.

Copland's flirtation with jazz was illustrated by Michael Collins in the Clarinet Concerto, written for Benny Goodman in 1948. The opener was the Fanfare for the Common Man, while Slatkin closed with the Four Dance Episodes from Rodeo. The comforting familiarity of these pieces was fascinatingly reinterpreted by the less- celebrated riches of the other works on the programme.